This investigation is designed to provide information about fundamental physical and chemical variables which modify flow in the microcirculation, especially in capillaries. Delivery of oxygen and plasma-borne constituents to tissues and removal of products of metabolism depend on movement of red blood cells and plasma through capillaries. Flow in capillaries is dependent primarily upon pressure gradients, non-adherence of red blood cells, flexibility of red blood cells and the composition of plasma. Representative techniques and studies to be used in this investigation include 1) cinematographic recording and analyses of cinefilm records using both conventional rates of framing and high speed photography, 2) end stage development and application of cineholography both at conventional rates of framing and up to 3000 frames per second, 3) experimental alterations of coagulation factors, fibrinolytic factors and immune system components of blood with evaluation by cinematographic and cineholographic techniques of effects of microcirculatory flow, 4) application of a technique developed for perfusion of the mesenteric circulation to the study of the influence of abnormal cells and abnormal plasma on capillary and larger vessel flow, 5) application of dye markers, fluorescent markers and radioisotope labelling and counting to the measurement of capillary permeability, 6) investigation of the possible roles of both platelets and leucocytes in control of capillary permeability and 7) further exploration of an apparent participation of leucocytes in hemostasis.